Certain 2-acetylpyridinethiosemicarbazones have been described to have anti-malarial or anti-bacterial activity; U.S. Pat. Nos. 4,317,776, 4,493,930, and 4,385,055, J. Med. Chem. 22, 855 (1979), J. Med. Chem. 22, 1373 (1979). These references also describe the chemical preparation of certain important active ingredients of the present invention. The references do not disclose the use of the chemical compounds in animal feed compositions or their use to increase feed efficiency in meat-producing animals such as poultry. The useful quantities of the active ingredients in the present invention are lower than the anti-bacterial levels which are described as useful in the prior art.